Process for producing improved crystals of 3-amino-2-hydroxyacetophenone salt

Abstract

The present invention concerns a process for producing crystals of 3-amino-2-hydroxyacetophenone salt having a high bulk density and improved flow properties, by treating 3-amino-2-hydroxyacetophenone of formula (1) <IMAGE> or hydrogen halide salt thereof with sulfuric acid, in a solvent.

What is claimed is: 
     
       1. A process for producing crystals of 3-amino-2-hydroxyacetophenone salt which have high bulk density of from about 0.5 to about 10 ml/g and an angle of repose of not larger than 60 degrees, which comprises the step of treating 3-amino-2-hydroxyacetophenone of the formula (1) ##STR5## or hydrogen halide salt thereof with sulfuric acid, in a solvent. 
     
     
       2. A process according to claim 1, wherein said 3-amino-2-hydroxyacetophenone or hydrogen halide salt thereof is 3-amino-2-hydroxyacetophenone or the hydrochloride salt thereof. 
     
     
       3. A process according to claim 1, wherein 1 to 10 moles of sulfuric acid is used per one mole of said 3-amino-2-hydroxyacetophenone or hydrogen halide salt thereof. 
     
     
       4. A process according to claim 1, wherein an amount of sulfuric acid is 2 to 4 moles per one mole of said 3-amino-2-hydroxyacetophenone or hydrogen halide salt thereof. 
     
     
       5. A process according to claim 1, wherein said solvent consists essentially of an alcohol or an aromatic hydrocarbon. 
     
     
       6. A process according to claim 1, wherein said solvent contains at least 70% by weight of an alcohol or an aromatic hydrocarbon. 
     
     
       7. A process according to claim 1, wherein said solvent consists essentially of an alcohol. 
     
     
       8. A process according to claim 1, wherein said solvent contains at least 70% by weight of an alcohol. 
     
     
       9. A process according to claim 1, wherein said crystals of 3-amino-2-hydroxyacetophenone salt produced have a bulk density of from 0.5 to 6 ml/g. 
     
     
       10. A process according to claim 1, wherein said crystals of 3-amino-2-hydroxyacetophenone salt produced have a bulk density of from 0.5 to 4 ml/g. 
     
     
       11. A process according to claim 1, wherein said 3-amino-2-hydroxyacetophenone and/or hydrogen halide salt thereof to be treated with sulfuric acid is obtained by reducing a nitro compound represented by formula (2) ##STR6## wherein X represents a halogen atom or hydrogen atom in the presence of a catalyst. 
     
     
       12. A process according to claim 1, wherein said 3-amino-2-hydroxyacetophenone and/or hydrogen halide salt thereof used as starting product is obtained by reducing a nitro compound represented by formula (2) ##STR7## wherein X represents a halogen atom or hydrogen atom, in the presence of a catalyst, and subsequently removing said catalyst. 
     
     
       13. A process according to claim 12, wherein a base is added to the reaction mixture after reducing said nitro compound but before removing said catalyst. 
     
     
       14. A process according to claim 13, wherein the base is selected from the group consisting of alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, alkaline earth metal bicarbonates, alkali metal carboxylates, alkaline earth metal carboxylates, alkali metal hydroxides, alkaline earth metal hydroxides, alkyl amines, pyridines and ammonia. 
     
     
       15. A process according to claim 1, wherein the angle of repose is not larger than 55 degrees. 
     
     
       16. A process according to claim 15, wherein the angle of repose is not larger than 50 degrees. 
     
     
       17. A method of raising the bulk density of 3-amino-2-hydroxyacetophenone salt crystals to about 0.5 ml/g to about 10 ml/g, which comprises the step of contacting 3-amino-2-hydroxyacetophenone of the formula (1) ##STR8## or hydrogen halide salt thereof with 30 to 98% sulfuric acid or fuming sulfuric acid, in a solvent, wherein the resulting 3-amino-2-hydroxyacetophenone salt crystals have an angle of repose of not larger than 60 degrees. 
     
     
       18. A method of improving the flow property of 3-amino-2-hydroxyacetophenone salt crystals, which comprises the step of contacting 3-amino-2-hydroxyacetophenone of the formula (1) ##STR9## or hydrogen halide salt thereof with sulfuric acid, in a solvent at a temperature of from about -20° C. to 100° C. or to the boiling point of the solvent, wherein the resulting 3-amino-2-hydroxyacetophenone salt crystals have an angle of repose of not larger than 60 degrees and a bulk density of about 0.5 to about 10 ml/g. 
     
     
       19. A method according to claim 17, wherein said angle of repose is not larger than 55 degrees. 
     
     
       20. A method according to claim 19, wherein said angle of repose is not larger than 50 degrees. 
     
     
       21. A method according to claim 18, wherein said angle of repose is not larger than 55 degrees. 
     
     
       22. A method according to claim 21, wherein said angle of repose is not larger than 50 degrees.